The present invention relates to an expansion joint system that can be utilized in highway construction where gaps are formed between adjacent concrete sections. The expansion joints of the present invention find particular applicability in bridge constructions, roadway construction and other structures where large movements in multiple directions must be accommodated.
A gap is purposely provided between adjacent concrete structures for accommodating dimensional changes within the gap occurring as expansion and contraction due to temperature changes, shortening and creep caused by prestressing, seismic cycling and vibration, deflections caused by live loads, and longitudinal forces caused by vehicular traffic. An expansion joint is conventionally utilized to accommodate these movements in the vicinity of the gap.
Bridge constructions are also subject to relative movement in response to the occurrence of seismic events. This raises particular problems, because the movements occurring during such events are not predictable either with respect to the magnitude of the movements or with respect to the direction of the movements. In many instances bridges have become unusable for significant periods of time, due to the fact that traffic cannot travel across damaged expansion joints.
The difficulty in designing such expansion joints is that when a movement component of large magnitude is applied transverse to the roadway direction, the joints are typically unable to accommodate these movements. Attempts have been made to avoid this problem, as described, for example, in U.S. Pat. No. 4,674,912. This expansion joint system, which is sold by Maurer Sohne, GmbH, attempts to deal with the problem by using sliding and swiveling movements of the joint components to accommodate the non-longitudinal movements.
U.S. Pat. No. 4,120,066 to Leroux discloses an expansion joint for adjacent roadway sections to accommodate expansion or contraction of the distance between the adjacent concrete roadway sections, which utilizes a lazy tongs device.
U.S. Pat. No. 5,887,308 to Walter also discloses an expansion joint system for accommodating movement with an expansion joint.
The “Steelflex” system offered by D.S. Brown Company utilizes a center beam, which is individually attached to its own support bar. The support bars move parallel to the direction of movement of the structure.
The “Robek System” offered by Tech Star, Inc. includes a modular joint system designed to accommodate longitudinal movement. As with the other prior art systems, this design has not been proven effective to prevent significant damage under substantial seismic event conditions.
Therefore, a need still exists in the art for an improved expansion joint system that can accommodate large movements that occur separately or simultaneously in multiple directions in the vicinity of a gap having an expansion joint between two adjacent roadway sections, for example, movements occurring in longitudinal and transverse directions relative to the flow of traffic, which may be caused by thermal changes, prestressing, seismic events, and vehicular deflections.